One of the difficulties that beginners of a musical instrument face is learning how to play chords. Especially in playing a keyboard instrument, when a player wants to play chords that are different in tonality, the player needs to arrange a pressing form of chords, in other words, form of player's fingers to press keys in completely different ways, since the keyboard instrument has black keys and white keys. Such complications make learning chords difficult.
Some conventional techniques have been proposed that enable players who do not know anything about sheet music of a keyboard instrument to visually remember chords as patterns. For example, Unexamined Japanese Patent Application Kokai Publication No. 2005-84068 discloses a technique for sequentially showing circularly-arranged notes constituting one octave of a keyboard, and showing constituent notes of a target chord so as to be distinguishable from the other constituent notes.
However, the above-described conventional technique has a problem of requiring time for users to convert the circular arrangement of the notes to arrangement of a keyboard in users' heads. In addition, the technique also has a problem that only one chord can be shown at a time. For this reason, users cannot understand relationship between a major chord (major), a minor chord (minor), a seventh chord (seventh), a suspended-second chord (sus2), a suspended-fourth chord (sus4), an added-ninth chord (add9), and the like, even though the users can understand pitches corresponding to each chord.